Nitric oxide in patients with schizophrenia: the relationship with the severity of illness and the antipsychotic treatment

bjectives: Past studies regarding the relationship between nitric oxide and schizophrenia have reported controversial results. Consequently, the aims of this study are i) to analyze the differences in nitric oxide concentration between patients with schizophrenia and healthy controls, ii) to investigate the influence of antipsychotic treatment on nitric oxide, iii) to correlate nitric oxide concentration with severity of illness, and iv) to investigate the relationship between nitric oxide and any personality disorder. Research design and methods: We recruited 24 patients and 24 controls; the sample was divided into three groups of 8 patients, each according to the pharmacological treatment (haloperidol, olanzapine, or risperidone). The severity of illness was assessed by PANSS and personality traits were evaluated by SCID II. A blood sample was taken to assess the plasma concentration of nitrites and nitrates. Results: Patients presented higher nitrate levels than controls (p < 0.05); subjects under olanzapine reported lower nitrate levels than those treated with risperidone (p < 0.05) or haloperidol (p < 0.001). Nitrate levels were correlated with PANSS total score (rho = 0.748; p < 0.001), but not with SCID II scores. Conclusions: Despite the fact that this study found a correlation between PANSS score and nitrate levels, it is unclear whether nitric oxide is related to the severity of schizophrenia, because nitrate levels are also affected by antipsychotic treatment.